Engine with rotating detonation combustion system

ABSTRACT

A Brayton cycle engine including an inner wall assembly defining a detonation combustion region upstream thereof extended from a longitudinal wall into a gas flowpath. An actuator adjusts a depth of the detonation combustion region into the gas flowpath. A method for operating the engine includes flowing an oxidizer through the gas flowpath; capturing a portion of the flow of oxidizer via the inner wall; flowing a first flow of fuel to the captured flow of oxidizer; producing a rotating detonation gases via a mixture of the first flow of fuel and the captured flow of oxidizer; flowing at least a portion of the detonation gases downstream to mix with the flow of oxidizer; flowing a second flow of fuel to the mixture of detonation gases and oxidizer; and burning the mixture of the second flow of fuel and the detonation gases/oxidizer mixture.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.15/904,918 filed on Feb. 26, 2018, the contents of which are herebyincorporated by reference in their entirety.

FIELD

The present subject matter is related to continuous detonationcombustion systems for Brayton cycle machines.

BACKGROUND

Propulsion systems, including gas turbines, ramjets, and scramjets,often use deflagrative combustion systems to burn a fuel/oxidizermixture to produce combustion gases that are expanded and released toproduce thrust. While such propulsion systems have reached a high levelof thermodynamic efficiency through steady improvements in componentefficiencies and increases in pressure ratio and peak temperatures,further improvements are nonetheless welcome in the art.

More particularly, further improvements are desired in stabilization ofthe combustion process generally. More specifically, furtherimprovements are desired for combustion systems applied in gas turbineaugmentor/afterburner or inter-turbine burner systems, ramjets, andscramjets.

BRIEF DESCRIPTION

Aspects and advantages of the invention will be set forth in part in thefollowing description, or may be obvious from the description, or may belearned through practice of the invention.

The present disclosure is directed to a Brayton cycle engine and amethod for operation. The engine includes a longitudinal wall extendedalong a lengthwise direction. The longitudinal wall defines a gasflowpath of the engine. An inner wall assembly is extended from thelongitudinal wall into the gas flowpath. The inner wall assembly definesa detonation combustion region in the gas flowpath upstream of the innerwall assembly. An actuator configured to adjust a cross sectional areaof the gas flowpath adjusts a depth of the detonation combustion regioninto the gas flowpath. The method for operating the engine includesflowing an oxidizer through a gas flowpath into a combustion section;capturing a portion of the flow of oxidizer via an inner wall extendedinto a depth of the gas flowpath; flowing a first flow of fuel to theportion of the flow of oxidizer captured via the inner wall; producing arotating detonation wave of detonation gases via a mixture of the firstflow of fuel and the portion of oxidizer upstream of the inner wall;flowing at least a portion of the detonation gases downstream and mixingthe detonation gases with the flow of oxidizer; flowing a second flow offuel to the mixture of detonation gases and the flow of oxidizer; andburning the mixture of the second flow of fuel, the detonation gases,and the flow of oxidizer to produce thrust.

In various embodiments, the method for operating the engine includesadjusting a cross sectional area of the gas flowpath based on anoperating condition of the engine. In one embodiment, adjusting thecross sectional area of the gas flowpath includes adjusting one or moreof a pressure, flow, or temperature of the first flow of fuel based atleast on an operating condition of the engine. In another embodiment,the operating condition of the engine is based at least on a pressure,temperature, or flow rate of the flow of oxidizer at the combustionsection. In still various embodiments, adjusting the cross sectionalarea of the gas flowpath includes adjusting a depth into the gasflowpath of the inner wall based at least on an operating condition ofthe engine. In one embodiment, adjusting the depth of the inner wallinto the gas flowpath is between approximately 0% and approximately 35%of the depth of the gas flowpath. In another embodiment, adjusting thedepth of the inner wall into the gas flowpath is further based at leaston a desired minimum number of detonation cells to produce the rotatingdetonation wave.

In one embodiment of the method for operating the engine, burning themixture of the second flow of fuel, the detonation gases, and the flowof oxidizer to produce thrust includes a deflagrative combustionprocess.

In another embodiment, the flow of oxidizer at the combustion sectiondefines a supersonic axial velocity through the gas flowpath producingan oblique shockwave from the flow of oxidizer in the gas flowpath.

In various embodiments, the method for operating the engine furtherincludes adjusting a profile of the oblique shockwave based on anoperating condition of the engine. In one embodiment, adjusting theprofile of the oblique shockwave includes adjusting a depth into the gasflowpath of the inner wall.

In still various embodiments, the actuator is coupled to the inner wallassembly. The actuator adjusts the depth of the inner wall assembly inthe gas flowpath. In one embodiment, the actuator extends the inner wallassembly between approximately 0% and approximately 35% of a depth ofthe gas flowpath. In still other embodiments, the inner wall assemblyincludes an upstream face extended from the longitudinal wall into thegas flowpath, and a downstream face extended from the longitudinal walland coupled to the upstream face in the gas flowpath. The downstreamface is disposed at an angle relative to the longitudinal wall. In oneembodiment, the actuator adjusts the angle of the downstream facerelative to the longitudinal wall. In another embodiment, the downstreamwall is between approximately 10 degrees and approximately 80 degreesrelative to the longitudinal wall. In still another embodiment, theupstream face of the inner wall assembly defines the first fuelinjection port providing a first flow of fuel to the detonationcombustion region. In still yet another embodiment, the downstream faceof the inner wall assembly defines the second fuel injection portproviding a second flow of fuel downstream of the detonation combustionregion. In various embodiments, the longitudinal wall defines the firstfuel injection port providing a first flow of fuel to the detonationcombustion region.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdescription and appended claims. The accompanying drawings, which areincorporated in and constitute a part of this specification, illustrateembodiments of the invention and, together with the description, serveto explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including thebest mode thereof, directed to one of ordinary skill in the art, is setforth in the specification, which makes reference to the appendedfigures, in which:

FIGS. 1A-1B are lengthwise cross sectional views of exemplaryembodiments of a two dimensional configuration engine according to anaspect of the present disclosure;

FIGS. 2A-2B are lengthwise cross sectional views of exemplaryembodiments of an axisymmetric configuration engine according to anaspect of the present disclosure;

FIG. 3A is a cross sectional view of an exemplary embodiment of the twodimensional configuration engine of FIGS. 1A-1B along section 3A-3A;

FIG. 3B is a cross sectional view of an exemplary embodiment of theaxisymmetric configuration engine of FIG. 2A along section 3B-3B;

FIG. 3C is a cross sectional view of an exemplary embodiment of theaxisymmetric configuration engine of FIG. 2B along section 3C-3C;

FIG. 4 is a detailed lengthwise cross sectional view of an exemplaryembodiment of a combustion section of the engines generally provided inFIGS. 1A-1B and FIGS. 2A-2B according to an aspect of the presentdisclosure;

FIGS. 5A-5B are detailed lengthwise cross sectional views of exemplaryembodiments of a combustion section of the engines generally provided inFIGS. 1A-1B and FIGS. 2A-2B according to an aspect of the presentdisclosure;

FIG. 6A is a lengthwise cross sectional view of an exemplary embodimentof a portion of the combustion section generally provided in FIG. 4 andFIGS. 5A-5B in a fully extended position;

FIG. 6B is a lengthwise cross sectional view of an exemplary embodimentof a portion of the combustion section generally provided in FIG. 6A ina partially extended position;

FIG. 7A is a lengthwise cross sectional view of an exemplary embodimentof a two dimensional configuration engine according to an aspect of thepresent disclosure;

FIG. 7B is a lengthwise cross sectional view of an exemplary embodimentof a axisymmetric configuration engine according to an aspect of thepresent disclosure;

FIG. 8A is a lengthwise cross sectional view of an exemplary embodimentof a portion of the combustion section generally provided in FIG. 4,FIGS. 5A-5B, and FIGS. 7A-7B in a fully extended position;

FIG. 8B is a lengthwise cross sectional view of an exemplary embodimentof a portion of the combustion section generally provided in FIG. 8A ina fully retracted position;

FIG. 9 is a detailed lengthwise cross sectional view of anotherexemplary embodiment of a combustion section of the engines generallyprovided in FIGS. 1A-1B, FIGS. 2A-2B, and FIGS. 7A-7B according to anaspect of the present disclosure;

FIG. 10A is a cross sectional view of the detailed view generallyprovided in FIG. 9 as an exemplary two dimensional configuration;

FIG. 10B is a cross sectional view of the detailed view generallyprovided in FIG. 9 as an exemplary axisymmetric configuration;

FIG. 11 is another exemplary axisymmetric cross sectional view of theengine according to an aspect of the present disclosure; and

FIG. 12 is a flowchart outlining exemplary steps of a method foroperating a Brayton cycle engine.

Repeat use of reference characters in the present specification anddrawings is intended to represent the same or analogous features orelements of the present invention. scramjets.

DETAILED DESCRIPTION

Reference now will be made in detail to embodiments of the invention,one or more examples of which are illustrated in the drawings. Eachexample is provided by way of explanation of the invention, notlimitation of the invention. In fact, it will be apparent to thoseskilled in the art that various modifications and variations can be madein the present invention without departing from the scope or spirit ofthe invention. For instance, features illustrated or described as partof one embodiment can be used with another embodiment to yield a stillfurther embodiment. Thus, it is intended that the present inventioncovers such modifications and variations as come within the scope of theappended claims and their equivalents.

As used herein, the terms “first”, “second”, and “third” may be usedinterchangeably to distinguish one component from another and are notintended to signify location or importance of the individual components.

The terms “forward” and “aft” refer to relative positions within a heatengine or vehicle, and refer to the normal operational attitude of theheat engine or vehicle. For example, with regard to a heat engine,forward refers to a position closer to a heat engine inlet and aftrefers to a position closer to a heat engine nozzle or exhaust.

The terms “upstream” and “downstream” refer to the relative directionwith respect to fluid flow in a fluid pathway. For example, “upstream”refers to the direction from which the fluid flows, and “downstream”refers to the direction to which the fluid flows.

The singular forms “a”, “an”, and “the” include plural references unlessthe context clearly dictates otherwise.

Approximating language, as used herein throughout the specification andclaims, is applied to modify any quantitative representation that couldpermissibly vary without resulting in a change in the basic function towhich it is related. Accordingly, a value modified by a term or terms,such as “about”, “approximately”, and “substantially”, are not to belimited to the precise value specified. In at least some instances, theapproximating language may correspond to the precision of an instrumentfor measuring the value, or the precision of the methods or machines forconstructing or manufacturing the components and/or systems. Forexample, the approximating language may refer to being within a 10percent margin.

Here and throughout the specification and claims, range limitations arecombined and interchanged. Such ranges are identified and include allthe sub-ranges contained therein unless context or language indicatesotherwise. For example, all ranges disclosed herein are inclusive of theendpoints, and the endpoints are independently combinable with eachother.

Embodiments of an engine and combustion section are generally providedthat improve combustion stability and performance for ramjet andscramjet engines, and gas turbine engines including inter-turbineburners or afterburning exhaust systems, or duct burners generally.Various embodiments of the engine generally provided herein define arotating detonation combustion region upstream of a main combustionprocess, such as a conventional or deflagrative combustion process. Invarious embodiments, the rotating detonation combustion region maygenerally act as a pilot burner for the downstream conventionalcombustion process, such as to improve stability and performance of thecombustion section of the engine. Furthermore, embodiments of the enginegenerally provided may effectuate a cross sectional area change of a gasflowpath via modulation of a fuel split between the rotating detonationcombustion region and the conventional combustion process, therebyenabling operation of the combustion section over a range or pluralityof dynamic pressures in the gas flowpath in contrast to an approximatelyconstant q-path.

Referring now to the drawings, FIGS. 1A-1B and FIGS. 2A-2B arelengthwise cross sectional views of an exemplary Brayton cycle engine(hereinafter, “engine 10”). Various embodiments of the engine 10 maydefine a ramjet, a scramjet, inter-turbine burner orafterburner/augmentor for a gas turbine engine, or duct burnergenerally. As such, though the engine 10 generally provided herein maysubstantially define a supersonic combustion ramjet or scramjet engine(e.g., FIG. 1A, FIG. 2A) or a subsonic combustion ramjet engine (e.g.,FIG. 1B, FIG. 2B), various embodiments may define a portion of anengine, such as a gas turbine engine, such as to provide inter-turbinethrust, afterburning thrust, or a multiple-cycle machine (e.g., a ramjetor scramjet integrated with a gas turbine engine).

Referring to FIGS. 1A-1B and FIGS. 2A-2B, the engine 10 defines an inletsection 20, a combustion section 100, and an exhaust section 30 inserial flow arrangement along a lengthwise direction L. The engine 10includes a longitudinal wall 110 extended along the lengthwise directionL. The longitudinal wall 110 defines, at least in part, a gas flowpath90 of the engine 10. For example, the longitudinal wall 110 is extendedalong the lengthwise direction L and contoured to define the combustionsection 100 of the engine 10. The longitudinal wall 110 may further beextended along the lengthwise direction L and contoured to define theinlet section 20 of the engine 10.

For example, referring to FIGS. 1A-1B and FIGS. 2A-2B, the inlet section20 is generally contoured to admit a flow of oxidizer, shownschematically by arrows 81, into the engine 10 to flow through the gasflowpath 90 to the combustion section 100. In FIG. 1A and FIG. 2A, theengine 10 generally defines a scramjet engine, such as to admit asupersonic flow of oxidizer 81 into the gas flowpath 90 of the engine 10and maintain an axial velocity greater than Mach 1 at the combustionsection 100. In FIG. 1B and FIG. 2B, the engine 10 generally defines aramjet engine, such as to admit a flow of oxidizer 81 into the engine10, including a supersonic flow. However, the longitudinal wall 110defines contours such as to retard the flow of oxidizer 81 upstream ofthe combustion section 100 to a subsonic axial velocity (i.e., less thanMach 1), such as generally depicted at contour 21.

Referring still to FIG. 1B, the longitudinal wall 110 of the engine 10generally depicted further defines contours such as to define a nozzle31 at the exhaust section 30. The nozzle 31 accelerates a flow ofcombustion gases through the gas flowpath 90, shown schematically byarrows 82, from the combustion section 100 to generate thrust. Thenozzle 31 may define a convergent nozzle or a convergent-divergentnozzle based at least on a desired range of operating air speed of theengine 10.

In the embodiments generally provided in FIGS. 1A-1B, the engine 10defines a two-dimensional configuration, such as further detailed inregard to FIG. 3A depicting an exemplary cross sectional embodiment atsection 3A-3A of FIGS. 1A-1B. As generally depicted in FIG. 3A, theexemplary two-dimensional configuration of the engine 10 defines a widthW and a height H. In the embodiments generally provided in regard toFIGS. 1A-1B and FIG. 3A, the longitudinal wall 110 may further extendalong the width W and the height H, such as to define a substantiallyrectangular cross section of the gas flowpath 90. As another example,width W and height H may be approximately equal such as to define asubstantially square cross sectional area.

In other embodiments, such as generally provided in FIGS. 2A-2B, theengine 10 defines a generally axisymmetric configuration relative to areference axial centerline 12 extended along the lengthwise direction L.Further cross sectional embodiments at section 3B-3B (FIG. 2A) andsection 3C-3C (FIG. 2B) are generally depicted and described in regardto FIGS. 3B-3C. In various embodiments, such as generally provided inregard to FIGS. 2A-2B and FIGS. 3B-3C, the longitudinal wall 110 mayextend annularly around the axial centerline 12, such as to define asubstantially circular or annular cross section of the gas flowpath 90.

Referring now to FIGS. 1A-1B, FIGS. 2A-2B and FIGS. 3A-3C, and furtherin conjunction with the exemplary detailed views provided in FIG. 4, theengine 10 further includes an inner wall assembly 120 extended into thegas flowpath 90. The inner wall assembly 120 partially blocks orcaptures a portion of the flow of oxidizer 81 at an upstream face 121 ofthe inner wall assembly 120, such as shown schematically by arrows81(a). The inner wall assembly 120 defines a region, shown schematicallyat circle 125, upstream of the inner wall assembly 120. Moreparticularly, a region 125, such as defining a sheltered cavity, isdefined adjacent to the upstream face 121 and the longitudinal wall 110.A first flow of fuel, shown schematically by arrows 78, is mixed withthe captured portion of oxidizer 81(a) at the region 125 (shown anddescribed further in regard to FIGS. 5A-5B). This fuel-oxidizer mixtureis then ignited with a high-energy source to setup a detonation wave,such as shown schematically by arrows 127 in FIGS. 3A-3C.

Referring still to FIG. 4, in conjunction with FIGS. 1A-1B, FIGS. 2A-2B,and FIGS. 3A-3C, a portion of the detonation gases from the detonationwave 127 (FIGS. 3A-3C), shown schematically by arrows 126, exits theregion 125 and mixes with the flow of oxidizer 81(b) not captured in theregion 125 by the inner wall assembly 120. As the detonation gases 126and oxidizer 81(b) flow downstream of the upstream face 121 of the innerwall assembly 120, a second flow of fuel, shown schematically by arrows79, is provided through a downstream wall 122 of the inner wall assembly120 into the gas flowpath 90. The detonation gases 126, oxidizer 81(b),and fuel 79 are mixed and burned to produce combustion gases 82 thatfurther provide thrust as previously described herein. In variousembodiments, the mixture of detonation gases 126, oxidizer 81(b), andfuel 79 may be mixed and burned as a deflagrative combustion process ora detonative combustion process.

The inner wall assembly 120 such as described herein may improvestabilization of the downstream combustion process including theoxidizer 81(b) and the second flow of fuel 79 by controlling theproduction of detonation gases 126 via controlling a flow rate of thefirst flow of fuel 78 provided to the detonation process within theregion 125. For example, the first flow of fuel 78 and the portion ofoxidizer 81(a) may together alter a fuel/oxidizer mixture downstream ofthe inner wall assembly 120. As another example, the inner wall assembly120 capturing the portion of oxidizer 81(a) and providing the first flowof fuel 78 may define a pilot burner control for the combustion section100 such as to improve overall combustion stability, performance, oroperability at various flow rates, pressures, or temperatures of theflow of oxidizer 81. As still another example, the inner wall assembly120 generally enables an independent aerodynamic method to provide anarea change along the gas flowpath 90 via changes in the first flow offuel 78, as well as changes in the first flow of fuel 78 relative to thesecond flow of fuel 79. As such, the inner wall assembly 120 enablesoperation of the engine 10 over a plurality of dynamic pressures of theflow of oxidizer 81 rather than being restricted to an approximatelyconstant volumetric flow rate through the gas flowpath 90.

Referring back to FIG. 4, the inner wall assembly 120 may further definea tip 119 extended into the gas flowpath 90. In various embodiments, thetip 119 is extended at least partially toward an upstream end of theengine 10 (i.e., toward the inlet section 20). The tip 119 may bedefined at an inward-most end of the upstream face 121 of the inner wallassembly 120 into the gas flowpath 90. For example, the tip 119 maygenerally be defined approximately where the upstream face 121 and thedownstream face 122 are coupled. In various embodiments, the tip 119defines a waveform extended along the width W and/or height H, i.e.,along the cross section at the length along the lengthwise direction Lrelative to two-dimensional embodiments such as generally provided inFIG. 3A. As other embodiments, the tip 119 defines a waveform extendedalong the annulus or circumferential direction C relative toaxisymmetric embodiments such as generally provided in FIGS. 3B-3C. Instill various embodiments, the tip 119 defines a sine wave, a trianglewave, a box wave, a saw tooth wave, or combinations thereof.

Referring back to the generally axisymmetric configurations of theengine 10 generally provided in regard to FIGS. 2A-2B and FIGS. 3B-3C,the longitudinal wall 110 may further define a first longitudinal wall111 defined radially outward of a second longitudinal wall 112. Each ofthe first longitudinal wall 111 and the second longitudinal wall 112 areconfigured substantially as shown and described in regard to thelongitudinal wall 110. For example, in one embodiment of the engine 10and longitudinal wall 110 such as generally shown in FIG. 2A and FIG.3B, the inner wall assembly 120 may extend into the gas flowpath 90 fromone or more of the first longitudinal wall 111 or the secondlongitudinal wall 112.

The inner wall assembly 120 extended from the first longitudinal wall111 may define a first rotating detonation combustion region 125(a). Theinner wall assembly 120 extended from the second longitudinal wall 112may define a second rotating detonation combustion region 125(b). Asgenerally depicted in FIG. 2A and FIG. 3B, the first region 125(a) isdefined generally along an outer radius proximate to the firstlongitudinal wall 111. The second region 125(b) is defined generallyalong an inner radius proximate to the second longitudinal wall 112.Referring to FIG. 3B, a first detonation wave 127(a) may propagatethrough the first region 125(a) and a second detonation wave 127(b) maypropagate through the second region 125(b).

In one embodiment, the first detonation wave 127(a) and the seconddetonation wave 127(b) propagate co-rotationally, i.e., the firstdetonation wave 127(a) and the second detonation wave 127(b) propagatealong the same circumferential direction C around the axial centerline12. In another embodiment, the first detonation wave 127(a) and thesecond detonation wave 127(b) propagate counter-rotationally, i.e., thefirst detonation wave 127(a) and the second detonation wave 127(b)propagate along the circumferential direction C around the axialcenterline 12 opposite of one another. In various embodiments, thedetonation wave 127 may propagate clockwise or counter-clockwise throughthe gas flowpath 90.

It should be appreciated that descriptions and depictions of detonationwave 127 herein and throughout generally apply to the first detonationwave 127(a) and the second detonation wave 127(b), unless otherwisespecified. Still further, it should be appreciated that descriptions anddepictions of longitudinal wall 110 herein and throughout generallyapply to the first longitudinal wall 111 and the second longitudinalwall 112, unless otherwise specified. Furthermore, it should beappreciated that descriptions and depictions of the region 125 hereinand throughout generally apply to the first region 125(a) and the secondregion 125(b), unless otherwise specified.

Referring now to FIGS. 5A-5B, further exemplary embodiments of a portionof the combustion section 100 of the engine 10 generally depicted inFIGS. 1A-1B, 2A-2B, 3A-3C, and 4A-4B, are generally provided. Theembodiments depicted in FIGS. 5A-5B further detail embodiments of afirst fuel injection port 124 providing the first flow of fuel 78 and asecond fuel injection port 123 providing the second flow of fuel 79 suchas previously described herein. In various embodiments, the second fuelinjection port 123 is defined through the downstream wall 122 of theinner wall assembly 120 to provide the second flow of fuel 79. Forexample, the second fuel injection port 123 provides the second flow offuel 79 generally at or downstream of the inner wall assembly 120. Thesecond fuel injection port 123 may generally provide the second flow offuel 79 to mix with the flow of oxidizer 81(b) for a conventional ordeflagrative combustion process. In various embodiments, theconventional combustion process downstream of the detonative combustionregion 125 may define a main burner or combustion process, such as toenable high power or maximum power operation of the engine 10. In stillvarious embodiments, the first fuel injection port 124 is independentlycontrollable from the second fuel injection port 123, such as to providea pressure, flow, or temperature of the first flow of fuel 78 differentfrom the second flow of fuel 79.

In one embodiment of the engine 10, the first fuel injection port 124 isdefined through the longitudinal wall 110. For example, the first fuelinjection port 124 may be defined through the longitudinal wall 110upstream of the inner wall assembly 120 such as to provide the firstflow of fuel 78 approximately perpendicular to the flow of oxidizer 81through the gas flowpath 90 into the region 125. As another example, thefirst fuel injection port is defined generally adjacent to the region125, such as upstream and adjacent to the upstream face 121 of the innerwall assembly 120.

In another embodiment of the engine 10, the first fuel injection port124 is defined through the upstream face 121 of the inner wall assembly120. For example, the first fuel injection port 124 may be definedthrough the upstream face 121 such as to provide the first flow of fuel78 into the region 125 approximately parallel to the flow of oxidizer 81through the gas flowpath 90. In various embodiments, the upstream face121 is disposed at an angle relative to the direction of flow ofoxidizer 81 through the gas flowpath 90. As such, the first fuelinjection port 124 may further be defined at an acute angle relative tothe direction of flow of oxidizer 81 through the gas flowpath 90, suchas generally corresponding to the acute angle of the upstream face 121.

Referring to the exemplary embodiment providing in FIG. 5A, the upstreamface 121 is extended into the gas flowpath 90, such as along the depthD. In one embodiment, the upstream face 121 is defined substantiallyconcave. For example, the upstream face 121 protrudes toward thedownstream face 122. The concaved upstream face 121 may define a pocketor sheltered cavity promoting the region 125 at which the detonationwave 127 (FIGS. 3A-3C) propagates. Referring to FIGS. 5A-5B, a point orportion at which the upstream face 121 and the downstream face 122 arecoupled may be approximately equal to (e.g., FIG. 5B) or forward (e.g.,FIG. 5A) along the lengthwise direction L of a point or portion at whichthe upstream face 121 and the longitudinal wall 110 are coupled. Assuch, the upstream face 121 of the inner wall assembly 120 may enablecapturing the portion of flow of oxidizer 81(a) to generate thedetonation wave 127 (FIGS. 3A-3C) within the region 125.

Referring to the exemplary embodiment generally provided in FIG. 5B, theupstream face 121 may extend substantially inward into the gas flowpath90. For example, the upstream face 121 may extend approximatelyperpendicular from the longitudinal wall 110 into the gas flowpath 90.In other embodiments, such as where the longitudinal wall 110 is oblique(i.e., not parallel) to the reference lengthwise direction L, theupstream face 121 may extend approximately perpendicular into the gasflowpath 90 relative to the reference lengthwise direction L. As such,an angle 129 between the longitudinal wall 110 and the upstream face 121may be between approximately 45 degrees and approximately 135 degrees.In various embodiments, the angle 129 may be approximately 90 degrees.

Referring now to the embodiments generally provided in FIG. 4 and FIGS.5A-5B, the upstream face 121 may extended from the longitudinal wall 110along a reference depth D into the gas flowpath 90. In variousembodiments, such as defining a two dimensional gas flowpath 90 of theengine 10 generally provided in FIGS. 1A-1B, the reference depth D isbased on the height H or the width W (FIGS. 3A-3C) of the gas flowpath90. The upstream face 121 of the inner wall assembly 120 is extendedinto the gas flowpath 90 at reference depth D based on a minimum numberof cells required to sustain rotating detonation at the region 125. Thedetonation cell is characterized by a cell width (X) that depends on thetype of fuel (e.g., liquid or gas hydrogen or hydrocarbon fuel, orcombinations thereof) and oxidizer (e.g., air or oxygen) as well as thepressure and temperature of the reactants (i.e., fuel 78 and oxidizer81(a)) at the region 125 and the stoichiometry (4)) of the reactants.For each combination of fuel 78 and oxidizer 81(a), cell size decreaseswith increasing pressure and temperature, and for stoichiometry greaterthan or less than 1.0. As the cell width may decrease by 20 times ormore from a lowest steady state operating condition to a highest steadystate operating condition, the flow rate of fuel 78 is modulated basedat least on a pressure, flow, or temperature of the oxidizer 81(a)entering the region 125 such as to provide a sustainable detonation cellsize across the plurality of operating conditions of the engine 10.

Still further, the first flow of fuel 78 may be modulated based on adesired location into which the fuel 78 enters the region 125. Forexample, in one embodiment, the first fuel injection port 124 may bedefined through the upstream face 121 and the longitudinal wall 110. Assuch, fuel 78 may be modulated through the upstream face 121 and thelongitudinal wall 110 such as to define different fuel splits or flowrates through each of the upstream face 121 or longitudinal wall 110.

Referring still to FIGS. 5A-5B, in one embodiment, the upstream face 121is extended from the longitudinal wall 110 into approximately 35% orless of the gas flowpath 90 along the reference depth D. Alternatively,the upstream face 121 is extended from the longitudinal wall 110 intothe gas flowpath 90 equal to or less than approximately 35% of depth D.Still further, the upstream face 121 is extended from the longitudinalwall 110 into the gas flowpath 90 equal to or less than approximately35% of depth D relative to approximately a portion of the gas flowpath90 along the lengthwise direction L from which the upstream face 121 isextended from the longitudinal wall 110.

In regard to two-dimensional embodiments of the engine 10, such asgenerally provided in FIGS. 1A-1B and FIG. 3A, the reference depth D maybe based on the height H (FIG. 3A). In other two-dimensional embodimentsof the engine 10, the reference depth D may be based on the width W(FIG. 3A). In regard to generally axisymmetric embodiments of the engine10, such as generally provided in FIGS. 2A-2B and FIGS. 3B-3C, thereference depth D may be a radial distance from an inner radius (e.g.,at an inner second longitudinal wall 112) to an outer radius (e.g., atan outer first longitudinal wall 111).

In various embodiments, the upstream face 121 is extended from thelongitudinal wall 110 into the gas flowpath 90 equal to or less thanapproximately 20% of depth D. In still yet various embodiments, theupstream face 121 is extended from the longitudinal wall 110 into thegas flowpath 90 equal to or less than approximately 13% of depth D. Instill another embodiment, the upstream face 121 is extended from thelongitudinal wall 110 into the gas flowpath 90 equal to or less thanapproximately 7% of depth D.

Referring still to the exemplary embodiments generally provided in FIGS.5A-5B, the downstream face 122 of the inner wall assembly 120 may extendat an acute angle 128 from the longitudinal wall 110 toward the upstreamface 121. In various embodiments, the angle 128 is between approximately10 degrees and approximately 80 degrees. In still various embodiments,the angle 128 is between approximately 30 degrees and approximately 60degrees. It should be appreciated that in other embodiments (not shown),the downstream face 122 may further define a convex or concave wallprotruding into the gas flowpath 90 or toward the upstream face 121.

Referring now to FIGS. 6A-6B, further exemplary embodiments of thecombustion section 100 of the engine 10 are generally provided. Theexemplary embodiments depicted in FIGS. 6A-6B are configuredsubstantially similarly as shown and described in regard to FIGS. 1A-1B,FIGS. 2A-2B, FIGS. 3A-3C, FIG. 4, and FIGS. 5A-5B (as such, features andreference numerals shown on the aforementioned figures may notnecessarily be transposed to FIGS. 6A-6B). The embodiments depicted inFIGS. 6A-6B generally depict the inner wall assembly 120 as providing anadjustable depth D through the gas flowpath 90. For example, FIG. 6Adepicts the inner wall assembly 120 as fully extended into the gasflowpath 90. As another example, FIG. 6B depicts the inner wall assembly120 as partially extended into the gas flowpath 90. As previouslydescribed, the inner wall assembly 120 is extended into the gas flowpath90 at depth D based on a minimum number of detonation cells required tosustain rotating detonation at the region 125.

In various embodiments, the engine 10 further includes an actuator 150coupled to the inner wall assembly 120 to adjust the depth D of theinner wall assembly 120 in the gas flowpath 90. The actuator 150 mayextend the inner wall assembly 120, or more specifically, the upstreamface 121, to approximately 35% of the depth D of the gas flowpath 90from the longitudinal wall 110. The actuator 150 may further contractthe inner wall assembly 120, or more specifically, the upstream face121, to approximately 0% of the depth D of the gas flowpath 90. As such,the actuator 150 may contract the inner wall assembly 120 to beapproximately flush to the longitudinal wall 110.

Furthermore, actuation or articulation of the inner wall assembly 120may further be based on a desired angle 128 of the inner wall assembly120, or more specifically, the downstream face 122, into the gasflowpath 90. Adjusting the angle 128 may further adjust an angle atwhich the second fuel injection port 123 (FIGS. 5A-5B) is disposed intothe gas flowpath 90 relative to the flow of oxidizer 81(b).

In one embodiment, the inner wall assembly 120 may adjust its depth Dinto the gas flowpath 90 via pivoting at the point or portion at whichthe downstream face 122 is coupled to the longitudinal wall 110. Forexample, the angle 128 at which the downstream face 122 is extended fromthe longitudinal wall 110 may be adjusted to increase or decrease thedepth D at which the upstream face 121 is extended into the gas flowpath90. In another embodiment, and further in regard to axisymmetricembodiments of the engine 10 generally provided in regard to FIGS.2A-2B, the inner wall assembly 120 may adjust its depth D into the gasflowpath 90 via actuating or articulating at least partially along thetangential or circumferential direction C relative to the axialcenterline 12 or gas flowpath 90 annulus. Still further, the actuator150 coupled to the inner wall assembly 120 may dispose the inner wallassembly 120 at least partially along the tangential or circumferentialdirection C.

In still various embodiments, such as further in regard to supersoniccombustion or scramjet embodiments generally described and depicted inregard to FIG. 1A and FIG. 2A, the inner wall assembly 120 defining thedetonation wave region 125 may further affect the oblique shockstructure produced from the supersonic flow of oxidizer 81 through thegas flowpath 90. For example, modulation of the first flow of fuel 78 tothe region 125 will affect the oblique shock structure across aplurality of operating conditions of the engine 10. Still further, theactuating or articulating inner wall assembly 120 will also affect theoblique shock structure across the plurality of operating conditions ofthe engine 10. As such, affecting the oblique shock may be used toimprove combustion stability and performance of the engine 10.

Referring now to FIGS. 7A-7B, further exemplary embodiments of theengine 10 are generally provided. The exemplary embodiments generallyprovided in regard to FIGS. 7A-7B are configured substantially similarlyas shown and described in regard to FIGS. 1A-1B, FIGS. 2A-2B, FIGS.3A-3C, FIG. 4, FIGS. 5A-5B, and FIGS. 6A-6B. More specifically, FIGS.7A-7B generally depict supersonic combustion configurations of theengine 10, in which the flow of oxidizer 81 enters the combustionsection 100 at a speed at or above Mach 1. Still more specifically, FIG.7A depicts a generally two-dimensional configuration of the engine 10,such as shown and described in regard to FIGS. 1A-1B and FIG. 3A.Furthermore, FIG. 7B depicts a generally axisymmetric configuration ofthe engine 10, such as shown and described in regard to FIGS. 2A-2B andFIGS. 3B-3C.

The embodiments of the engine 10 depicted in FIGS. 7A-7B, and furtherdepicted in FIGS. 8A-8B, further include an upstream wall assembly 140disposed upstream along the lengthwise direction L of the inner wallassembly 120 and the region 125. The upstream wall assembly 140 iscoupled to the longitudinal wall 110 and extended into the gas flowpath90. The upstream wall assembly 140 may further include a first face 141extended from the longitudinal wall 110 into the gas flowpath 90 and asecond face 142 extended from the longitudinal wall 110 and coupled tothe first face 141.

Referring now to FIGS. 8A-8B, the upstream wall assembly 140 may actuateor articulate into and out of the gas flowpath 90 such as to adjust thedepth D of the first face 141. For example, FIG. 8A depicts the upstreamwall assembly 140 fully extended into the gas flowpath 90. FIG. 8Bdepicts the upstream wall assembly 140 fully extended out of the gasflowpath 90. The upstream wall assembly 140 may alter an amount of theflow of oxidizer 81 that enters the region 125 (i.e., the amount ormagnitude of the portion of oxidizer 81(a)) to generate the detonationwave 127 (FIGS. 3A-3C). Altering the flow of oxidizer 81(a) to theregion 125 may be based on the operating condition of the engine 10. Forexample, the upstream wall assembly 140 may extended or contract fromthe longitudinal wall 110 to control an intensity or magnitude of thedetonation wave 127, or the portion of detonation gases 126 mixed withthe flow of oxidizer 81(b) and fuel 79 to produce combustion gases 82.

Referring now to FIG. 9, a lengthwise cross sectional view of anembodiment of the combustion section 100 is generally provided.Referring further to FIGS. 10A-10B and FIG. 11, additional crosssectional views of embodiments of the combustion section 100 aregenerally provided. The embodiments generally provided in FIG. 9, FIGS.10A-10B, and FIG. 11 are configured substantially similarly as shown anddescribed in regard to FIG. 4 and FIGS. 3A-3B, respectively. However, inFIG. 9 and FIGS. 10A-10B, the combustion section 100 further includes astrut 130 extended between the longitudinal walls 110 into the gasflowpath 90. Still further, the inner wall assembly 120 is extended fromthe strut 130 into the gas flowpath 90. In various embodiments, such asdepicted in FIGS. 10A-10B and FIG. 11, the inner wall assembly 120 iscoupled to the longitudinal wall 110 and the strut 130 such as to definea plurality of the region 125 bounded by the longitudinal wall 110 andthe strut 130.

For example, in one embodiment, the strut 130 is extended along theheight H (FIG. 10A) across the gas flowpath 90 and is coupled to thelongitudinal wall 110 opposite along the height H (FIG. 10A). As anotherexample, in the embodiment generally provided in FIG. 10B, the strut 130is extended between an outer radius of the longitudinal wall 110 and aninner radius of the longitudinal wall 110 along the depth D across thegas flowpath 90. More specifically, the strut 130 may extend between thefirst longitudinal wall 111 at an outer radius and the secondlongitudinal wall 112 at an inner radius.

Each strut 130 generally defines a plurality of the region 125 anddetonation wave 127 generally fluidly segregated from one another. Forexample, the combustion section 100 defines a quantity of generallyfluidly segregated regions 125 equal to one greater than the quantity ofstruts 130. Stated alternatively, quantity n struts 130 generatesquantity n+1 regions 125. Each of the plurality of regions defines adetonation wave 127 therethrough generally fluidly segregated from oneanother adjacent regions 125.

Referring still to FIG. 9, FIGS. 10A-10B, and FIG. 11, the struts 130enable generating and controlling a plurality of detonation zone regions125 at the combustion section 100. Each region 125 defines a separatedetonation wave 127 within it. Furthermore, each region 125 provides aportion of detonation gases 126 out of the region 125 to mix with theoxidizer 81(b) and fuel 79. In various embodiments, each region 125 mayinclude a separately controllable flow of fuel 78 from two or more ofthe first fuel injection port 124 (FIG. 5A-5B). As such, the struts 130may enable defining a plurality of distinct detonation zone regions 125such as to adjust a temperature profile downstream of the region 125within the gas flowpath 90. For example, the plurality of regions 125may adjust a temperature profile across the height H and/or width W orgenerally across the depth D such as to reduce a temperature gradientacross the gas flowpath 90, the longitudinal wall 110, or both. Reducingthe temperature gradient may improve durability of the engine 10, reducedeterioration or wear of the engine 10, and generally improvereliability.

In various embodiments, the strut 130 includes a forward wall 131, anaft wall 132, and an axial wall 133. The forward wall 131 and the aftwall 132 are each extended through the depth D of the gas flowpath 90between the longitudinal walls 110. The axial wall 133 is extended alongthe lengthwise direction L between the forward wall 131 and the aft wall132. The forward wall 131 and the aft wall 132 are extended between thelongitudinal walls 110 along the depth D of the gas flowpath 90. Forexample, the forward wall 131 and the aft wall 132 may each extend alongthe height H (FIG. 10A and FIG. 11) defining the depth D of the gasflowpath 90. As another example, the forward wall 131 and the aft wall132 may each extend along the depth D of the gas flowpath 90 between thefirst longitudinal wall 111 and the second longitudinal wall 112.

The forward wall 131 of the strut 130 and the upstream face 121 of theinner wall assembly 120 may together define a groove or cavity at whichthe detonation region 125 is disposed, such as to define a circuitthrough which the detonation wave 127 propagates. For example, theforward wall 131 may extend from the longitudinal wall 110 from forwardof upstream of the upstream face 121 of the inner wall assembly 120. Theaft wall 132 may extend from the longitudinal wall 110 from downstreamor aft of the upstream face 121. In one embodiment, the aft wall 132 mayextend from approximately where the downstream face 122 of the innerwall assembly 120 and the longitudinal wall 110 are coupled.

Referring now to FIG. 11, an exemplary gas flowpath 90 view of theengine 10 from upstream viewed downstream is generally provided. Invarious embodiments, the strut 130 may extend at least partiallytangentially through the gas flowpath 90. For example, referring to theaxisymmetric configuration of the engine 10 generally provided in FIG.11, the strut 130 is extended partially along the circumferentialdirection C. As another example, the axial wall 133 of the strut 130 isextended at least partially along the circumferential direction C suchas to dispose the aft wall 132 at a different circumferentialorientation relative to the forward wall 131 each coupled to the axialwall 133. As such, the flow of oxidizer 81(b) and/or the combustiongases 82 (FIG. 9) across the struts 130 may further include a swirlalong the circumferential direction C.

Referring now to FIG. 12, a flowchart outlining exemplary methods foroperating a Brayton cycle engine is generally provided (hereinafter,“method 1000”). The exemplary steps generally provided herein may beimplemented in an engine such as described herein in regard to FIGS.1-11, and further referenced below. Although the steps outlined hereinmay be presented in a particular order, it should be appreciated thatthe steps of the method 1000 may be re-ordered, re-arranged,re-sequenced, omitted, or augmented without deviating from the presentdisclosure.

The method 1000 includes at 1002 flowing an oxidizer (e.g., oxidizer 81)through a gas flowpath (e.g., gas flowpath 90) into a combustion section(e.g., combustion section 100). At 1004, the method 1000 includescapturing a portion of the flow of oxidizer (e.g., oxidizer 81(a)) viaan inner wall (e.g., inner wall assembly 120) extended into a depth ofthe gas flowpath (e.g., depth D of gas flowpath 90). At 1006, the method1000 includes flowing a first flow of fuel (e.g., fuel 78) to theportion of the flow of oxidizer (e.g., oxidizer 81(a)) captured via theinner wall. At 1008, the method 1000 includes producing a rotatingdetonation wave (e.g., detonation wave 127) of detonation gases via amixture of the first flow of fuel and the portion of oxidizer upstreamof the inner wall. At 1010, the method 1000 includes flowing at least aportion of the detonation gases (e.g., detonation gases 126) downstreamand mixing the detonation gases with the flow of oxidizer (e.g.,oxidizer 81(b)). At 1012, the method 1000 includes flowing a second flowof fuel (e.g., fuel 79) to the mixture of detonation gases and the flowof oxidizer. At 1014, the method 1000 includes burning the mixture ofthe second flow of fuel, the detonation gases, and the flow of oxidizerto produce combustions gases (e.g., combustion gases 82) to producethrust.

In various embodiments, the method 1000 further includes at 1016adjusting a cross sectional area of the gas flowpath based on anoperating condition of the engine. In one embodiment, adjusting thecross sectional area of the gas flowpath includes at 1018 adjusting oneor more of a pressure, flow, or temperature of the first flow of fuelbased at least on an operating condition of the engine. In anotherembodiment, the operating condition of the engine is based at least on apressure, temperature, or flow rate of the flow of oxidizer at thecombustion section.

In still various embodiments, adjusting the cross sectional area of thegas flowpath includes at 1020 adjusting a depth into the gas flowpath ofthe inner wall based at least on an operating condition of the engine.In one embodiment, adjusting the depth of the inner wall into the gasflowpath is between approximately 0% and approximately 35% of the depthof the gas flowpath. In another embodiment, adjusting the depth of theinner wall into the gas flowpath is further based at least on a desiredminimum number of detonation cells to produce the rotating detonationwave.

In one embodiment, burning the mixture of the second flow of fuel, thedetonation gases, and the flow of oxidizer to produce thrust comprises adeflagrative combustion process. In another embodiment, the flow ofoxidizer at the combustion section defines a supersonic axial velocitythrough the gas flowpath producing an oblique shockwave from the flow ofoxidizer in the gas flowpath.

In various embodiments, the method 1000 further includes at 1022adjusting a profile of the oblique shockwave based on an operatingcondition of the engine. In one embodiment, adjusting the profile of theoblique shockwave includes at 1024 adjusting a depth into the gasflowpath of the inner wall. In another embodiment, adjusting the profileof the oblique shockwave includes at 1026 adjusting a depth into the gasflowpath of the upstream wall (e.g., upstream wall assembly 140).

In still various embodiments, the method 1000 further includes at 1028adjusting the flow of oxidizer to the inner wall via an upstream wall(e.g., upstream wall assembly 140) disposed upstream of the inner wall.In one embodiment, adjusting the cross sectional area of the gasflowpath further includes at 1030 adjusting a depth into the gasflowpath of the upstream wall based at least on an operating conditionof the engine.

The embodiments of the engine 10, combustion section 100, and method1000 generally shown and described herein may improve combustionstabilization of ramjet and scramjet engines and gas turbine engineinter-turbine or afterburner combustion systems. Various embodiments ofthe engine 10 and combustion section 100 generally provided hereinprovide an independent aerodynamic structure and method to produce across sectional area change across the gas flowpath 90 via modulation oradjustment of an amount of fuel 78 provided to the detonation combustionregion 125 versus an amount of fuel 79 provided for conventional ordeflagrative combustion downstream of the detonation region 125. Forexample, the embodiments generally shown and described herein may enablea gas flowpath 90 cross sectional area change over a plurality ofoperating conditions of the engine 10 (e.g., different pressure, flowrate, temperature, etc. of the flow of oxidizer 81 into the engine 10).As such, the embodiments generally shown and provided may enable theengine 10 to effectually provide a variable volumetric flow rate of theflow of oxidizer 81 (or, more specifically, flow of oxidizer 81(b)) forconventional combustion (i.e., via fuel 79 downstream of the inner wallassembly 120) different from a volumetric flow rate of the flow ofoxidizer 81 entering the engine 10 at the inlet section 20.

Additionally, embodiments of the engine 10 and method 1000 mayeffectuate a cross sectional area change to produce a variablevolumetric flow rate of the flow of oxidizer to the combustion section100 for mixing and combustion with fuel 79 with generally passive ornon-moving structures, such as via modulation of the first flow of fuel78 to mix with a portion of the flow of oxidizer 81(a) to producedetonation gases 126 at the detonation region 125. For example, theinner wall assembly 120 may define a detonation region 125 to capture aportion of the flow of oxidizer 81(a) and produce detonation gases 126.Modulation of the fuel 78 to produce the detonation gases 126 influencesor stabilizes the conventional or deflagrative combustion processfurther downstream via the second flow of fuel 79, the flow of oxidizer81(b), and mixed with the detonation gases 126.

Additionally, or alternatively, embodiments of the engine 10 may provideactive structures to effectuate changes in a cross sectional area of thegas flowpath 90, such as via the upstream wall assembly 140. Inconjunction with the inner wall assembly 120 and modulation of the firstflow of fuel 78 to the detonation region, the upstream wall assembly 140may influence or stabilize the downstream conventional or deflagrativecombustion process.

Still further, the inner wall assembly 120, the upstream wall assembly140, or both may define an oblique shockwave from the flow of oxidizer81 through the gas flowpath 90. For example, the oblique shockwave mayincrease a pressure or temperature of the flow of oxidizer 81 toward acenter of the gas flowpath 90 (e.g., mid-span of depth D). As such, theoblique shockwave further improves or stabilizes the downstreamconvention or deflagrative combustion process.

Furthermore, the inner wall assembly 120 providing the first flow offuel 78 to the detonation region 125 may further improve stabilizationof the combustion section 100 at relatively low power operatingconditions. For example, a relatively low flow of oxidizer 81 into theengine 10 may be utilized to mix with the fuel 78 and produce detonationgases 126 and thrust at conditions that may generally be too low orunstable for a conventional or deflagrative combustion process via thesecond flow of fuel 79 mixed with the flow of oxidizer 81(b).

Still furthermore, embodiments of the combustion section 100 generallyprovided herein may decrease a lengthwise dimension of the engine 10 viaimproved combustion performance and stability. As such, embodiments ofthe engine 10, such as ramjet, scramjet, inter-turbine burner, orafterburner/augmentor systems may be improved or integrated intoapplications heretofore generally limited by known sizes or lengths ofsuch engines or apparatuses to which the engine is installed.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they include structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

1. A method for operating a Brayton cycle engine, the method comprising:flowing an oxidizer through a gas flowpath into a combustion section;capturing a portion of the flow of oxidizer via an inner wall extendedinto a depth of the gas flowpath; flowing a first flow of fuel to theportion of the flow of oxidizer captured via the inner wall; producing arotating detonation wave of detonation gases via a mixture of the firstflow of fuel and the portion of oxidizer upstream of the inner wall;flowing at least a portion of the detonation gases downstream and mixingthe detonation gases with the flow of oxidizer; flowing a second flow offuel to the mixture of detonation gases and the flow of oxidizer; andburning the mixture of the second flow of fuel, the detonation gases,and the flow of oxidizer to produce thrust.
 2. The method of claim 1,further comprising: adjusting a cross sectional area of the gas flowpathbased on an operating condition of the engine.
 3. The method of claim 2,wherein adjusting the cross sectional area of the gas flowpathcomprises: adjusting one or more of a pressure, flow, or temperature ofthe first flow of fuel based at least on an operating condition of theengine.
 4. The method of claim 2, wherein the operating condition of theengine is based at least on a pressure, temperature, or flow rate of theflow of oxidizer at the combustion section.
 5. The method of claim 2,wherein adjusting the cross sectional area of the gas flowpathcomprises: adjusting a depth into the gas flowpath of the inner wallbased at least on an operating condition of the engine.
 6. The method ofclaim 5, wherein adjusting the depth of the inner wall into the gasflowpath is between approximately 0% and approximately 35% of the depthof the gas flowpath.
 7. The method of claim 5, wherein adjusting thedepth of the inner wall into the gas flowpath is further based at leaston a desired minimum number of detonation cells to produce the rotatingdetonation wave.
 8. The method of claim 1, wherein burning the mixtureof the second flow of fuel, the detonation gases, and the flow ofoxidizer to produce thrust comprises a deflagrative combustion process.9. The method of claim 1, wherein the flow of oxidizer at the combustionsection defines a supersonic axial velocity through the gas flowpathproducing an oblique shockwave from the flow of oxidizer in the gasflowpath.
 10. The method of claim 9, further comprising: adjusting aprofile of the oblique shockwave based on an operating condition of theengine.
 11. The method of claim 10, wherein adjusting the profile of theoblique shockwave comprises: adjusting a depth into the gas flowpath ofthe inner wall. 12-20. (canceled)